This invention relates generally to explosion suppression apparatus and, more particularly, to apparatus for suppressing dust explosions.
The concern over grain industry dust explosions has grown rapidly in recent years. In addition to causing substantial property and monetary losses, such explosions have taken a heavy toll in personal injuries and fatalities. As a result, a serious need exists for improved systems to prevent or limit dust explosions.
A dust explosion consists essentially of pressure produced by the rapid burning of dust in air. The maximum pressure produced and the speed of pressure build-up (rate of pressure rise) are responsible for the damage caused by the explosion. The rate of burning of the dust cloud is affected by particle size, the ease of ignition, heat of combustion of the dust, and the concentration of dust in the air. When an explosion occurs in a grain elevator, a series of reports resembling a roll of thunder is usually heard. This is due to the fact that several explosions follow one another so rapidly that the report of one blends in with that of the next, making a continuous roar. For example, the original, or primary, explosion may occur in a cleaning machine where the dust cloud is confined in a relatively small space. The pressure and percussion from this primary explosion throws into suspension the dust which has accumulated on beams, ledges, and floors. This dust is ignited by the flame of the primary explosion, giving rise to the second explosion, which in turn, stirs up the dust in the surrounding portion of the elevator. Thus, the explosion is propagated through the elevator, or as far as dust is held in suspension or capable of being thrown in suspension.
The most effective technique for preventing dust explosion damage entails the rapid release of an explosion suppressant in response to the detection of an incipient explosion. A familiar suppressant is the halogen Halon 1301 which is typically stored under pressure and released at high velocity to create an inert atmosphere which will not support combustion. Although effective, prior suppression systems have been expensive to install and difficult to maintain and supervise in the troublesome environments that inherently accompany grain handling operations.
The object of this invention, therefore, is to provide an improved, less costly system for suppressing grain dust explosions.